1. Field of the Invention
The present invention is directed generally to methods and apparatus for holding a cutting tool for an automatic machine tool.
2. Description of the Prior Art
Typical prior art toolholders are shown in the brochures entitled "C. J. Winter Model 108 Shavetool Holder" and "Davenport Ordering Guide - Screw Machine Tool Co., Inc." and in U.S. Pat. No. 2,364,320 to Schlitters. A cutting tool holder using micrometer adjusting screws for lateral and longitudinal positioning is shown in U.S. Pat. No. 3,566,723 to Oborne.
A typical prior art toolholder includes a supporting roller disposed opposite the cutting tool mounting fixture. That supporting roller, however, is fixed relative to the cutting tool mounting fixture once the distance therebetween has been adjusted to determine the finished dimension of the rotating workpiece. This can lead to an improper cutting of the workpiece as illustrated in the sequential series of FIGS. 1A-1C.
FIG. 1A schematically illustrates a rotating workpiece 10 prior to the same being engaged by a cutting tool.
In FIG. 1B a prior art toolholder 12 has engaged the workpiece 10. The toolholder 12 is schematically illustrated and includes a supporting roller 14, a cutting tool mounting fixture 16, and a cutting tool 18. The supporting roller 14 is carried by a cradle or other support structure 20.
In FIG. 1B, a situation has been schematically illustrated wherein a center line 22 of the roller 14 is not exactly parallel to a top cutting edge 24 of the cutting tool 18, or to a center line 26 of the rotating workpiece 10. FIG. 1B illustrates the situation where the top edge 24 of the cutting tool 18 has been properly aligned parallel to the center line 26 of the workpiece 10. However, upon engagement of the roller 14 with the workpiece 10 the roller 14 has slightly bent or deflected the workpiece 16 so that a reduced diameter portion 28 thereof now lies parallel to the center line 22 of roller 14, but is no longer parallel to the top cutting edge 24 of cutting tool 18. This causes the cutting tool 18 to make a tapered cut on the reduced diameter portion 28, thus resulting in a defective finished part 10 as shown in FIG. 1C having a machined surface 30 which is tapered rather than being cylindrical as desired.
Thus, it is seen, that there is a need for a toolholder device which can overcome the problem of the prior art illustrated in FIGS. 1A-1C.
These same prior art toolholders also are very difficult to adjust for initial alignment of the cutting tool 18 with the workpiece 10. The prior art toolholders include a shaft attached to a head. The shaft has a flat portion defined thereon which is engaged by two opposed machine screws which are offset from a centerline of the shaft. To adjust the rotational position of the shaft about its centerline, both screws must be adjusted. This requires the machine operator to use both hands, advancing a screw on one side and retracting the opposing screw on the other side.
Thus, there is also a need for an improved means of adjusting the initial alignment of the cutting tool.